This invention relates to electrostatic imaging and in particular, to systems providing for real time imaging. A real time imaging system is described in U.S. Pat. No. 3,965,352 and the present invention is directed to an improvement suitable for use in a system of the type disclosed in said patent.
In the prior art real time imaging system, an electrostatic charge image is produced by X-rays in an X-ray absorber which produces electrons and positive ions that are moved in an electric field to produce the electrostatic charge image at an electrode. Toner particles are used to produce a visible image. The toner particles are dispersed in a liquid which is in contact with the electrode on which the electrostatic image is formed. After formation of the electrostatic image, the toner particles are selectively moved toward or away from the electrostatic image to form a toner image corresponding to the electrostatic image. The toner particle image is then viewed through a transparent electrode by reflected or scattered light. This system produces a visible image in real time and the system may be operated cyclicly to permit continuous observation of the object being X-rayed.
Another real time imaging system is disclosed in the copending application of John H. Lewis, entitled Low Light Level and Infrared Viewing System, Ser. No. 830,787, assigned to the same assignee as the present application. In this system, electrophoretic particles are dispersed in a liquid in a gap between electrodes and a photoresponsive layer at one electrode produces an electrostatic charge image at the surface of the gap opposite the other electrode, either directly or through some form of image intensifier.
When either system is operated cyclicly for continuous real time viewing, the image must be erased in preparation for the next exposure and image formation. Typically, the real time imaging system is operated at 10 cycles per second providing 10 separate frames or images per second. It is an object of the present invention to provide a new and improved system for erasing an image by discharging the electrostatic image prior to the following X-ray exposure.
These and other objects, advantages, features and results will more fully appear in the course of the following description.